JPH03204610A - Synchronizing signal check circuit for laser beam printer - Google Patents

Abstract

PURPOSE:To enable operation to continue without stopping a system by retrying the operation automatically in a device in case of synchronizing signal abnormality which occurs intermittently. CONSTITUTION:When a semiconductor laser 8 emits light and the period of a scan start signal does not become constant, a holding circuit is set as an error in the device, the light emission of the semiconductor laser 4 is stopped, and a scanner motor 8 is stopped from being driven. After it is confirmed that the stop of the scanner motor 8 is stopped, the scanner motor is actuated again and its stationary rotation is confirmed; and the semiconductor laser 4 is further made to emit light and the period of the scan start signal is checked. When the period is normal, printing operation is performed. When it is confirmed by a 2nd check that the period is normal, it is considered that the scanner motor 8 or a control system is abnormal, and then a host device is warned about a failure in operation as an error, and the device is stopped. Consequently, this device can be used continuously and the error which is to be generated intermittently can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a synchronization signal generation check circuit for a laser beam printer, and particularly to checking the periodicity of a synchronization signal generated at the start of scanning for each line. The synchronization signal generation for laser beam printers improves the output printing quality and allows the system to continue operating without stopping by automatically retrying the synchronization signal abnormality that occurs in the printer. Regarding check circuits.

[Conventional technology]

In conventional laser beam printers,
93219, one of the laser beams
The configuration is such that a synchronizing signal is generated at the starting point of line scanning. Therefore, the scanning start point can be detected normally.

In addition, as described in Japanese Patent Application No. 1983-2004, the number of laser beam clocks from the start point of one line of laser beam scanning to the start point of scanning of the next line is counted,
It is possible to check the normality of the number of dots, and the normality of the synchronization signal generation and the normality of the cycle are checked. If an abnormality occurs even once, it is immediately detected as an error.

[Problem to be solved by the invention]

With regard to abnormalities occurring in solids, the above conventional technology
Although it is effective, if the scanning start point that occurs in the intermittent is not detected or an error is detected due to an abnormal period of the synchronization signal that occurs in the intermittent, the device is immediately deemed to be abnormal and rendered unusable.

From the standpoint of reliability, it is necessary to prevent such errors from occurring, but no consideration is given to checking for errors that occur in the intermittent due to uneven motor rotation, noise, etc. There were problems with the error checking method and the error trial method.

SUMMARY OF THE INVENTION An object of the present invention is to perform an automatic retry in response to an intermittent synchronization signal generation abnormality, so that the device can continue to be used without being disabled.

[Means to solve the problem]

In order to achieve the above purpose, once the printing order is received,
Activate the drive motor for transporting the printing paper and the scanner motor for laser scanning and wait until they reach a constant rotation.
When a certain rotation is reached, a laser beam is emitted, and the periodicity of the synchronization signal generated at the start of scanning for each line is monitored over time.
When a scan start signal for the next line is generated within a specified time, it is considered normal, print data is received from the host device, and the print operation is started. If a scan start signal for the next line is not generated within a specified time, it is detected as an error and an error holding circuit is set.

The output of this error holding circuit causes the drive motor and scanner motor to stop, and after waiting for them to completely stop, the drive motor and scanner motor are started again, and as described above, the synchronization signal for each line is monitor the cycle,
When it is normal, the error holding circuit is reset and printing operation is started.

If an abnormality is detected during the re-check, it is determined that the abnormality has occurred in the solid, the error is detected, the device is stopped, the host device is notified that the laser beam printer is abnormal, and the received print command is abnormally terminated. It was designed so that

[Effect]

When a print command is received, the scanner motor is activated. Rotation of the scanner motor causes the polygon mirror to rotate. A laser beam is emitted by rotating a polygon mirror and scanned line by line. The generation cycle of the synchronization signal to start scanning one line is constant depending on the rotation speed of the scanner motor that drives the polygon mirror.As a result, the number of dots for emitting laser light within one cycle also becomes a constant value. , - Counts the number of laser beam dots from the generation of the synchronization signal to start scanning one line until the generation of the synchronization signal to start scanning the next line, and also uses a separate timer to calculate the cycle time of the synchronization signal and the laser beam. You can check the number of dots. Further, when the time elapsed by the timer is detected due to uneven rotation, noise, etc. due to an abnormality in the synchronization of the scanner motor, if a synchronization signal for the next line is not generated, an error is detected as a cycle abnormality and held. The output signal from this holding circuit causes the scanner motor to stop driving and start the scanner motor again. The generation cycle of the synchronization signal is checked in the same way as in the above procedure, and if an error is detected again, the process is abnormally terminated as an error. When no error is detected, printing is started and data can be received normally, so there will be no malfunction.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is an explanatory diagram showing an outline of a laser beam printer. As shown in the figure, laser light emitted from a semiconductor laser 4 passes through a lens 6 and is reflected by a polygon mirror 5 that is rotated in the direction of arrow E by a scanner motor 8. The laser beam reflected by the polygon mirror 5 passes through the lens 7 and hits the photosensitive drum 1 to form an image. The photosensitive drum 1 is rotated in the direction of arrow F by a drive motor (not shown), and
The laser beam scans in the direction of arrow H. A synchronizing signal at the scanning start point of one line is generated by reflecting a laser beam by a mirror 2 and detecting it by a detector 3.

FIG. 1 is a flowchart showing one embodiment of the present invention, FIG. 3 is a block diagram, and FIG. 4 is a time chart showing its operation.

In FIG. 1, when a print command is received from a host device,
Before starting the printing operation, drive the scanner motor 8,
The period of the encoder output signal output from the scanner motor 8 is checked to determine whether the rotation has become steady. Next, the semiconductor laser 4 is caused to emit light to check whether the period of the scan start signal for printing each line is a predetermined period. If this cycle is constant, paper feeding is started, data is received from the host device, and printing is executed. Generally, in order to keep the scanner motor 8 in steady rotation, the rotation speed and phase are controlled.If the rotation speed is high, the rotation speed is slowed down, and if the rotation speed is low, the speed is increased based on the encoder output signal. For more detailed rotation control, phase control is used to ensure a constant rotation and a constant phase. When performing this control, a hunting phenomenon in which the rotational speed fluctuates may occur due to poor control during synchronization pull-in or the like. This occurs when the rotation speed is not constant and the control is repeated to speed up and slow down, and only occurs when the scanner motor 8 is started. Furthermore, when this hunting phenomenon occurs, it often cannot be recovered unless it is forcibly stopped. Therefore, the semiconductor laser 8
When the period of the scanning start signal is not constant when the scanning start signal is emitted, a holding circuit is set as an error in the apparatus, and the emission of the semiconductor laser 4 is stopped and the driving of the scanner motor 8 is stopped. After confirming that the scanner motor 8 has stopped, the scanner motor is started again, and as described above, steady rotation is confirmed, and the semiconductor laser 4 is caused to emit light to check the period of the scan start signal. If the cycle is normal, print operation is executed. If the cycle is abnormal even after the second check, it is determined that the scanner motor 8 or the control system is abnormal and an error is detected, and the host device is notified that it is inoperable and the device is stopped.

Details will be explained with reference to the block diagram of FIG. 3 and the time chart of FIG. 4.

The scanning start signal A is output from the detector 3 shown in FIG. 2, and is output for each line.

Clock B is a clock signal that causes laser light to be emitted.

When the laser beam printer receives the print command a, it sets the flip-flop 26 to hold the command.The output signal of the flip-flop 26 sets the flip-flop 27 to rotate the scanner motor.This output signal causes the scanner motor to rotate. The drive circuit 28 is activated to rotate the scanner motor 8.

The rotational frequency check circuit 29 checks the rotational speed using the encoder output signal 5 generated by the rotation of the scanner motor 8, and the output signal e is used as feedback to the scanner motor drive circuit 28 to control the rotation to a steady state. When the scanner motor 8 reaches steady rotation, the rotation period check circuit 29 outputs a steady rotation signal.

The steady rotation signal opens the AND gate 10, and the scan start signal A passes through the AND gate 10 to reset the counter 11, drive the delay one shot 16, and generate the LINE 5YNC signal to start the -line scan. The reset counter 11 counts up with the clock B that causes the semiconductor laser 4 to emit light. A count value for one line scanning is set in the counter 12, and a comparison circuit 13 compares the count value of the counter 11 and the count value of the counter 12.
When the setting values of are compared and they match, a match signal K is outputted, and when the scan start signal for the next line comes, the AND gate 25 is established, the flip-flop 14 is set, and the FF14Q signal is outputted. On the other hand, the delay one-shot 16 driven by the scan start signal A outputs the pulse L after a predetermined period of time has elapsed. One shot 17 receives this pulse L and outputs pulse M. This pulse M resets the flip-flop 20 via the output signal Q of the flip-flop 14 and the AND gate 15. When the count values do not match, the output signal K of the comparison circuit 13 is not generated, the AND gate 25 is not opened, and the flip-flop 14 is not set, so when the pulse M is generated, the condition of the AND gate 15 is not satisfied and the signal R is Out flip flop 2
0 remains set. This flip flop 2
If 0 remains set, an error has been detected. The one-shot 18 is operated by the pulse M signal and a pulse N is output. This pulse N is applied to the flip-flop 14
Reset. Also, in case of error, flip-flop 20
The AND condition is satisfied with the output signal S, and the signal T is outputted via the AND gate 21. When no error occurs, the AND condition is not satisfied and the signal T is not output. When signal T is output, flip-flop 2 is activated as the first error.
Set and hold 2. Further, the signal T (ERI) resets the flip-flop 27 that rotates the scanner motor 8 and stops the scanner motor 8. A circuit (not shown) monitors the encoder output signal of the scanner motor 8, detects that the scanner motor 8 has stopped when the encoder output disappears, and then switches the flip-flop 2 again.
7 and rotate the scanner motor 8. Check the rotation period of the scanner motor in the same way as above, and if it is normal, generate the signal C and reset the flip-flop 22.
At 7, move on to the next action. When the rotation period is abnormal, the signal T from the AND gate 21 is output in the same manner as described above. Since this is the second error, the output signal of the flip-flop 22 and the conditions of the AND gate 23 are satisfied, and the flip-flop 24 is set to output ER2. When this ER2 is output, it is determined that the device is abnormal, and the device is stopped and the host device is notified that the device is abnormal.

According to this embodiment, it is possible to reliably detect synchronization signal abnormality errors that indicate the scanning start point due to scanner motor rotation abnormalities that occur in solids, and it is also possible to reliably detect rotation abnormality errors due to hunting, etc. when starting the scanner motor. can be detected. Furthermore, when an error occurs, instead of making the push device unusable, it is possible to continue operating the printer by automatically retrying the error that occurs in the intermittent, not in the system, but within the printer itself.

〔Effect of the invention〕

According to the present invention, when the cycle of the synchronization signal indicating the scanning start point is abnormal due to an abnormal rotation of the scanner motor, etc., instead of making the pushing device unusable, an automatic retry is performed within the device so that the device can continue to be used. By doing this, you can avoid errors that occur in the interim tent. Furthermore, errors that occur in solids can be reliably detected as errors. Therefore, it is possible to provide a laser beam printer that can perform highly reliable and stable printing without reducing system efficiency.

[Brief explanation of drawings]

FIG. 1 is a flow chart of an embodiment of the present invention, FIG. 2 is a diagram showing an outline of a laser beam printer, and FIG. 3 is a diagram showing an outline of a laser beam printer.
Operational block diagram of the embodiment shown in FIG. 4(a)(b)
is a time chart diagram. 1: Photosensitive drum, 2: Mirror, 3: Detector, 4: Semiconductor laser, 5: Polygon mirror, 6: Lens, 7: Lens, 8: Scanner motor. Compilation f Figure diagram number bi#! V Collection! Rin + Figure (α) (b)

Claims (1)

[Claims] 1. In the synchronization signal generation check circuit of a laser beam printer that checks the periodicity of the synchronization signal generated when the laser beam passes the scanning start point, from the time the above synchronization signal is generated until the next synchronization signal is generated. A counting means for counting the number of clocks for one scan, a holding means for holding a predetermined number of clocks for one scanning, and the counted value of the counting means and the number of clocks held in the holding means are compared, and the two match. a comparison means for outputting a coincidence signal when the synchronization signal is output; a timer means for counting a predetermined time required for one scan after the synchronization signal is output; and a timer means for outputting a signal indicating the elapse of the predetermined time; a determining means for determining that the laser beam emission and scanning mechanism are operating normally if the coincidence signal is output when the signal indicating that the predetermined time has elapsed; , means for determining that the laser light emission and scanning mechanism is abnormal when the coincidence signal is not output, and outputting a synchronization signal abnormality;
When a holding circuit that holds it as an error and a synchronization signal abnormality are output, a means for stopping the drive system and laser scanning system of the device and a means for detecting the stop are provided in the same way as the print end sequence, and a means for detecting the stop is provided. After that, a means is provided to restart the device again using the print start sequence, and upon restarting, the periodicity of the synchronization signal is checked again. If it is normal, the operation is executed, and if it is abnormal, the error holding circuit is activated. 1. A synchronization signal generation check circuit for a laser beam printer, characterized in that the synchronization signal generation check circuit for a laser beam printer is provided with a determining means for determining that the second detection is an error, and reporting it as an error.